Motion activated firearm laser sight

ABSTRACT

The present invention is directed to a system that controls the automatic operation a laser in a sighting mechanism to detect a target. The laser is activated when the system detects vibrational motion that causes a piezoelectric strip to produce an electrical signal. The laser is deactivated after a predetermined time has elapsed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims benefit of U.S. provisional applicationSer. No. 60/412,832, filed Sep. 23, 2002, the disclosure of which ishereby incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to the activation of a laser beam for asighting mechanism.

BACKGROUND OF THE INVENTION

A variety of light beam assemblies have been disclosed as sighting aidsfor weapons. These assemblies are either mounted on or are an integralpart of the firearm. An illumination source is provided that projects anarrow beam of light in a direction parallel to the weapon's bore-sight.When the light beam and bore-sight are properly aligned, the bullet orother type of projectile will hit on or very close to the location ofthe light beam on the target.

Lasers are a preferred mechanism of generating light beams for sightingapplications. Lasers can be focused into a narrow beam with a very smalldivergence angle, so that they produce a small bright spot on the targettens to hundreds of yards from the light source. As used herein the word“laser” is intended to include any form of a collimated light source.

The control devices for activating and deactivating the laser sight maybe located on various areas of the firearm such as on or near thehandgrip, rifle stock, or located somewhere on the trigger guard, andare incorporated into the electronic circuit of the laser. Thesecontrols may be switches, waterproof buttons, levers, latches, orslides, etc., however, they may prove to be awkward and be distractingto a user when the user has to activate the laser sight. For example,the user may have to use one of his/her gripping fingers to press anactivating button. Thus, the impulse to pull the trigger, which normallyis implemented without physical displacement of the barrel, may impartan unexpected twist to the weapon when one of the gripping fingers hasto hold or push a laser activator switch or button, thereby throwing thebullet off its intended course. This is particularly inconvenient to auser, such as a law enforcement officer, when suddenly confronted with ahostile and life threatening situation. The officer usually has toperform the following four steps when using a conventional laser-aimedweapon: 1) draw the weapon, 2) activate the laser, 3) aim, and ifnecessary, 4) fire.

To bypass the manual activation of the laser sight, a tritium switch hasbeen fitted into the trigger area of the weapon as described in U.S.Pat. No. 5,522,167. A vial containing the radioactive substance ismounted in the forward trigger guard housing and a photoelectric cell ismounted in the rear trigger housing so that it is aligned with theemission from the vial. Once the user picks up the weapon and placeshis/her finger on the trigger, the beam from the vial to the cell isinterrupted and the laser sight module is activated. The tritium switchcould be installed on any firearm that has a trigger guard and trigger.

A mercury switch has also been incorporated into the laser's circuitryto alleviate a user's manual control of the laser sight as described inU.S. Pat. No. 5,177,309. The mercury switch is located, in the case of apistol, in the handgrip of the firearm. The switch is responsive to theattitude of the weapon so as to be automatically activated, turns on thelaser sight, when the weapon is leveled at a target, and deactivated,turns off the laser sight, when it is not leveled, e.g., when thefirearm is substantially vertical in a belt holster.

Both the tritium and mercury switches eliminate an entire step from anofficer's list of activities needed to bring his/her weapon into actionagainst a perpetrator. These switches, however, include substances thatraise health and environmental issues.

SUMMARY OF THE INVENTION

The present invention provides a control system to operate a laser in asighting system for detecting a target. The control system is integratedin the laser sight's electronic circuitry and activates the laser byproducing an electrical signal. The signal is generated when the systemsenses vibrations caused by motion.

The above and other objects and advantages of the present invention willbe made apparent from the accompanying drawings and the descriptionthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description of the embodiments given below, serve toexplain the principles of the invention.

FIG. 1 is an illustration of a motion detector.

FIG. 2 is a circuit diagram of the circuitry included in the motiondetector of FIG. 1.

FIG. 3 is a representative schematic of a motion detector in a lasersight's circuitry.

FIG. 4 is a timing diagram illustrating the electrical behavior of thecircuitry of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As noted in the Background section, many types of firearms have lasersights or modules either mounted on an exterior surface of the firearmor incorporated within the firearm itself. Some of these firearms havecontrol buttons or switches to activate the laser sight on the exteriorsurface of the firearm. The user of the firearm has to manually activatethe laser thus adding an extra step to fire the weapon which may beawkward in a hostile situation. Other firearms have automatic switchesthat eliminate the manual activation of the laser by the user. Theseswitches, however, may pose health and environmental problems to theuser and society as a whole. The present invention is a system thatincorporates an environmentally friendly motion detector that activatesa laser sight on a firearm, and allows the user of the firearm to moreefficiently aim the weapon at a target.

The motion detector 10 of the present invention is shown in FIG. 1 whichis described in U.S. Pat. No. 5,612,670, and is expressly incorporatedby reference herein in its entirety. The motion detector 10, also knownas a mechanical shock detector, includes a printed circuit board 12 andoptionally may be encased within a plastic housing formed of two halves14 and 16. The housing halves may be secured together by an adhesive orby screws 19 that also allow the detector to be mounted on a firearmsuch as the bottom of a pistol grip or on a rifle stock. The circuitboard 12 is preferably manufactured using surface mount technology,thereby minimizing the size of the motion detector 10. The circuit board12 may be mounted in a laser sight assembly for a firearm or whenencased within a plastic housing elsewhere on or within the weaponitself.

The circuit board 12 includes a number of surface mounted components 18such as resistors, capacitors, diodes, transistors, and an integratedcircuit containing four operational amplifiers, as is more specificallydetailed in FIG. 2. Also included is a strip 17 of piezoelectricmaterial, a light-emitting diode (LED) D4, and a potentiometer RP3. Thecircuit board 12 is integrated into the laser sight's electroniccircuitry by connectors that are known to one skilled in the art. Anexample of such circuitry is shown in FIG. 3.

The motion detector 10 activates the laser sight of the firearm byproducing an electric signal produced by the piezoelectric strip 17. Thestrip 17 has piezoelectric crystals incorporated into its structure. Thecrystals generate a pulse of electricity in response to vibrationsproduced by motions which are sensed by the circuitry on the circuitboard. For example, in the present invention the motion detector 10 willactivate a laser sight on a pistol, or any other firearm with a lasersight, when the weapon is raised by the user to a horizontal position totake aim at a target. As described more below, if this electrical signalexceeds a threshold (which is preset by adjustment of correspondingpotentiometer RP3), the circuitry on circuit board 12 activates thelaser for a predetermined amount of time, for example from about 10 to30 seconds.

Three terminals 20, 24 and 26 lead from the circuit board 12. Theseterminals are connected to a power supply, such as the battery 30 for alaser, and a laser sight circuit. As discussed in more detail below,when a motion condition is triggered by circuit board 12, signals onthese terminals relay the motion condition to the laser sight circuit.Furthermore, light-emitting diode D4 is illuminated while the laser isactivated, thus providing a visual signal of a motion trigger, which canbe used during installation when adjusting potentiometer RP3 to selectthe appropriate threshold levels.

Referring to FIG. 2 and FIG. 3, the circuitry 13 on circuit board 12 ofthe motion detector 10 is configured for connection to a power supplysuch as is typically found to operate lasers. Power for the circuitboard 12 is obtained from the laser's battery 30 via connections toterminal 24 and terminal 26.

As illustrated in FIG. 2, a circuit 13 in accordance with principles ofthe present invention is configured for connection to and interactionwith a laser sight assembly. In accordance with principles of thepresent invention, terminal 20 is connected to the laser control 40.Inside of circuit 13, transistor Q3 is connected between terminal 20 andground. When transistor Q3 is active, the corresponding terminal 20 isconnected to ground, activating the laser sight circuit. When transistorQ3 is not active, resistor R20 pulls terminal 20 to the positive powersupply voltage.

Transistor Q3 is activated by analog circuitry which processeselectrical vibration signals produced by sensor 17, which may be forexample a piezoelectric strip available as part number 10027941 fromAmp, P.O. Box 3608, Harrisburg, Pa. 17105.

Sensor 17 is connected differentially across the input terminals of anoperational amplifier 42. Amplifier 42 produces a low-pass filteredversion 60 (FIG. 4) of the vibration signals from sensor 17 (low passfiltering is provided by capacitor C3 and resistor R5, the values ofwhich, when multiplied together, produce a time constant ofapproximately 3 milliseconds).

The filtered output of amplifier 42 is fed to the non inverting inputsof operational amplifier 46, which is wired as a comparator. Theinverting input of amplifier 46 is connected to the wiper ofpotentiometer RP3.

Thus, amplifier 46 compares the voltage of the filtered analog signalfrom amplifier 42 to a threshold voltage which is generated by adjustingpotentiometer RP3. If the filtered vibration signal from amplifier 42exceeds the threshold, the output of amplifier 46 saturates at thepositive supply voltage.

The output of amplifier 46 is not directly coupled to transistor Q3;instead, the output of amplifier 46 is connected to a sample-and-holdcircuit comprising two parallel diodes D5, a capacitor C7 and a resistorR19. Operational amplifier 48, which is wired as a comparator, comparesthe voltage of capacitor C7 at its inverting input to a referencevoltage at its non inverting input; the reference voltage is generatedby resistors R17 and R18, which are wired as a voltage divider andproduce a voltage of approximately one-sixth of the power supplyvoltage.

When the output of amplifier 46 is positive (indicating that thefiltered vibration signal from amplifier 42 exceeds the threshold set bypotentiometer RP3), capacitor C7 charges to a voltage near to the powersupply voltage. Because this capacitor voltage exceeds one-sixth of thepower supply voltage, the output of amplifier 48 saturates at the powersupply voltage. Amplifier 48 is connected to transistor Q3; thus, whenamplifier 48 saturates at the power supply voltage, transistor Q3 isactivated, triggering the laser control 40 via terminal 20.

If the filtered vibration signal from amplifier 42 falls below thethreshold set by potentiometer RP3, the output of amplifier 46 saturatesat the ground voltage. In this situation, diodes D5 turn off, andtherefore capacitor C7 remains charged near to the positive power supplyvoltage. Thus, even after the filtered vibration signal falls below thethreshold, amplifier 48 will remain saturated at the power supplyvoltage, and transistor Q3 will remain activated.

If, however, the filtered vibration signal remains below the thresholdset by potentiometer RP3 for any period of time, capacitor C7 willdischarge through resistor R19. The rate of discharge is determined bythe product of the values of resistor R19 and capacitor C7, and has atime constant from about 10 to about 30 seconds. Thus, if the filteredvibration signal remains below the threshold for longer than the presettime constant, capacitor C7 will discharge to a voltage less thanone-sixth of the power supply voltage. When this occurs, amplifier 48will as a result saturate at the ground voltage, and transistor Q3 willdeactivate and the laser will turn off.

The activation of the laser 22 may be controlled by a laser controlswitch 40 as illustrated in circuitry 23 in FIG. 3. When the controlswitch 40 is in the on position, the laser 22 is in a continuous stateof activation (continuously turned on) and deactivated (turned off) whenthe switch 40 is in the off position. When the switch 40 is in the autoposition, the activation of the laser 40 is controlled by the motiondetector 10. The laser 22 is activated when the motion detector senses avibration that creates an electrical signal that exceeds a presetthreshold and deactivated after a predetermined time period.

Referring to FIG. 4, in accordance with the forgoing, in response tomechanical shock producing a filtered vibration signal 60 from thepiezoelectric strip 17 having a burst of large magnitude oscillation,the circuit of FIG. 2 will produce an electrical ground connection online 20. (Trace 64 of FIG. 4 illustrates logically the state of thetransistor Q3 which connects to the trigger 2 terminal 20. An activetransistor state, during which a ground connection is being made, isindicated by a high or logic “1” value in the trace 64 of FIG. 4).

As can be seen in FIG. 4, trigger terminal 20 will be connected (viatransistor Q3) to ground for a period beginning whenever the filteredvibration signal 60 exceeds threshold 52, and continuing until thefiltered vibration signal 60 has not exceeded threshold 52 for a periodof time previously set.

Other variations or embodiments of the invention will also be apparentto one of ordinary skill in the art from the above description.Therefore, various changes, modifications or alterations to theseembodiments may be resorted to without departing from the spirit of theinvention and the scope of the following claims.

1. A control system for a laser mounted on a property comprising: alaser circuit, a motion detector functionally coupled to said lasercircuit for electrically detecting motion vibration and producing anelectrical signal representative of the motion vibration to activatesaid laser.
 2. The control system of claim 1 wherein said property is afirearm.
 3. The control system of claim 1 wherein said laser isactivated from about 10 seconds to about 30 seconds.
 4. The controlsystem of claim 3 wherein said laser is a laser sight for detecting atarget.
 5. The control system of claim 1 wherein said motion detector isa piezoelectric transducer.